Manufacturing of low alloy steel sucker rods by continuous process — heat treatment and characterization

Sucker rods are typically made of steel, and are important components of equipment such as reciprocating and progressive pumps used in various downhole applications in oil and gas wells. Chemical and mechanical characterizations were carried out on heat treated continuous sucker rods. These sucker rods were manufactured out of three types of steels by joining a series of coils together and subjecting them to continuous heat treatment during manufacturing. Tensile properties and hardness values were in the accepted ranges required by the operator. The fracture surfaces however demonstrated a shear type brittle fracture despite relatively high elongation-to-fracture. The fracture surface revealed unusual features in which very flat surfaces with sharp edges are present. Conventional sucker rods of grades H and D that were subjected to conventional heat treatments show completely different fracture mode. Comparison of microstructure and fracture surfaces of conventional and continuous sucker rods indicates that continuous rods were perhaps under-tempered, with insufficient tempering time.